Intro #

Before submitting your code for review, thoroughly testing it yourself ensures higher quality, reduces back-and-forth, and builds trust with your team. As an iOS developer, your goal is to catch UI inconsistencies, functional bugs, performance issues, and code quality problems early. This guide provides a comprehensive checklist to rigorously test your code, covering UI, functionality, performance, and code quality, tailored for iOS apps built with UIKit, SwiftUI, or hybrid stacks.

UI Testing #

Functional UI Testing #

1. Validate Against Design Specifications:

   • Compare your app’s UI pixel-by-pixel with Figma/Sketch/Zeplin designs. Use tools like Zeplin’s overlay feature or take screenshots to verify alignment, spacing, fonts, and colors.
   • Check Dynamic Type support for accessibility, ensuring text scales correctly for all text size settings (e.g., Accessibility Inspector in Xcode).
   • Test VoiceOver compatibility to confirm all UI elements are accessible, with proper labels and traits.

2. Positive Testing:

   • Validate happy paths (e.g., successful form submission, navigation flows). Ensure the UI behaves as expected under normal conditions.

3. Negative Testing:

   • Simulate error states (e.g., invalid inputs, network failures). Verify that error messages are clear, user-friendly, and properly displayed.

4. Destructive Testing:

   • Stress-test the UI by rapidly tapping buttons, switching screens, or interrupting animations to catch race conditions or duplicate network requests.

Non-Functional UI Testing #

1. Cross-Version and Cross-Device Testing:

   • Test on the minimum supported iOS version (e.g., iOS 14) and the latest (e.g., iOS 18). Use simulators or physical devices to catch version-specific issues, such as deprecated APIs or rendering bugs.
   • Verify UI on the smallest supported device (e.g., iPhone SE 1st Gen for iOS 14) and the largest (e.g., iPhone 16 Pro Max). Check for layout issues like truncation or clipping.

2. Theme and Orientation Testing:

   • Verify UI in both Light and Dark modes, checking for color contrast issues.
   • Test all supported device orientations (portrait, landscape) to ensure layouts adapt correctly.

3. Localization Testing:

   • If your app supports multiple languages, verify text rendering, truncation, and RTL layouts (e.g., Arabic, Ukrainian). Use Xcode’s scheme settings to switch languages.
   • Check for missing translations or hardcoded strings.

4. Edge Case Testing:

   • Test with low battery mode to ensure UI performance isn’t degraded.
   • Simulate poor network conditions (use Xcode’s Network Link Conditioner) to verify UI behavior during slow or dropped connections.
   • Test app behavior when interrupted (e.g., incoming calls, notifications, or app switching) to ensure UI state preservation and restoration.

Functional Testing #

1. Unit and UI Tests:

   • Run all existing XCTest cases to ensure your changes haven’t broken existing functionality. Write new unit tests for critical logic (e.g., view model calculations, API parsing).
   • Use XCUITest for end-to-end UI flows, especially for complex user journeys like onboarding or checkout processes.
   • Aim for at least 80% code coverage for new code, focusing on critical paths.

2. State Management:

   • Verify state persistence across app launches, especially for Swift Data, UserDefaults, or file-based storage.
   • Test background/foreground transitions to ensure data isn’t lost (e.g., save state when the app is backgrounded).

3. Networking:

   • Mock network responses to test success, failure, and edge cases.
   • Verify retry mechanisms and timeout handling for API calls.
   • Check offline support if applicable, ensuring cached data or offline modes work as expected.

4. Database Migration:

   • If your app uses Core Data, Swift Data or another database, verify migrations between schema versions. Test with sample data to ensure no data loss or corruption occurs.
   • Simulate upgrades from older app versions to confirm migration scripts execute correctly (e.g., use Core Data’s lightweight migration or custom mapping models).
   • Check for performance impacts during migration, especially with large datasets.

Performance Testing #

1. Memory and Leaks:

   • Use Xcode’s Instruments (Leaks, Allocations) to detect memory leaks and excessive memory usage. Pay attention to retain cycles in closures or delegates.
   • Test memory usage under stress (e.g., scrolling large lists, loading heavy assets).

2. Performance Profiling:

   • Use Instruments’ Time Profiler to identify slow methods or bottlenecks, especially in table/collection views or SwiftUI rendering.
   • Measure app launch time and optimize for <1 second startup (use Instruments’ App Launch template).
   • Test animations for smoothness, targeting 60 FPS (use Core Animation instrument).

3. Battery Usage:

   • Profile energy impact with Instruments’ Energy Log to ensure your app isn’t draining battery excessively (e.g., due to frequent network calls or heavy animations).

Code Quality #

1. Adhere to Team Standards:

   • Run SwiftFormat or SwiftLint to enforce team coding standards (e.g., naming conventions, file structure).
   • Follow architectural patterns (e.g., MVVM, VIPER) and principles like SOLID or DRY consistently.

2. Git Hygiene:

   • Review git diff between your branch and the target branch to catch unintended changes (e.g., debug logs, commented-out code, or unrelated files).
   • Write clear, concise commit messages that explain the why behind changes, not just the what.
   • Squash unnecessary commits to keep the history clean.

3. Code Readability and Maintainability:

   • Refactor complex methods into smaller, single-responsibility functions.
   • Add inline documentation (e.g., Swift DocC or /// comments) for public APIs or complex logic.
   • Remove dead code, unused assets, or deprecated API calls (use Xcode’s “Find Call Hierarchy” to verify usage).

4. Static Analysis:

   • Use Xcode’s static analyzer (Product > Analyze) to catch potential bugs like nullability issues or unhandled edge cases.
   • Address all warnings, treating them as errors to ensure a clean build.

Additional Tips #

1. Simulate Real-World Scenarios:

   • Verify push notification handling, including deep links and badge updates.
   • Test in Airplane Mode to ensure offline behavior is graceful.

2. Peer-Review Prep:

   • Create an MR/PR checklist in your tool (e.g., GitHub, GitLab, Bitbucket) with items like “Ran unit tests,” “Tested on iOS 14,” or “Verified Dark Mode.”
   • Document any known limitations or trade-offs in your MR/PR description to set clear expectations for reviewers.

3. Self-Review Checklist:

   • Create a personal checklist based on past review feedback to avoid repeating mistakes (e.g., “Did I remove TODOs?”).
   • Walk through your code as if you were the reviewer, reading it line-by-line to catch logical errors or unclear naming.